In a decision made public yesterday, Manhattan Civil Court Judge Norman Ryp tossed out a libel suit against Koch brought by Idris Kabia, who claimed the former mayor slandered him last year when he was the presiding judge on the popular TV show.

Kabia went on the show last March, when he was suing his son for $2,000 for allegedly failing to give him back some of his property. Koch ruled against the dad, who then had to settle for the $250 he got for appearing on the show.

But Kabia claimed Koch added insult to injustice by calling him a “kidnapper” who once stole his infant son away to Sierra Leone. Ryp, however, reviewed edited and unedited tapes of the show, and couldn’t find any mention of supposed slander.

And even if Koch did say it, it wouldn’t matter – the contract Kabia signed to go on the show recognized Koch as an arbitrator, and so he’s protected from civic liability, Ryp ruled.

Kabia couldn’t be reached. Koch told The Post his real-life counterpart was right on.